Splenic Artery Aneurysm: Causes and Management
All splenic artery aneurysms ≥2.0 cm in women of childbearing age (whether pregnant or not) and patients undergoing liver transplantation require immediate open repair or catheter-based intervention, while aneurysms ≥2.0 cm in other adults should probably undergo intervention. 1
Etiology
Splenic artery aneurysms are the most common visceral artery aneurysms, though hepatic artery pseudoaneurysms are increasingly recognized due to improved imaging 2. The primary causes include:
- Pancreatitis (most common cause of pseudoaneurysms - accounts for approximately 40-50% of cases) 3, 4
- Trauma (blunt or penetrating) 4
- Iatrogenic injury (percutaneous/laparoscopic procedures) 2, 4
- Pregnancy-related hemodynamic and hormonal effects 5
- Portal hypertension (including Caroli syndrome) 5
- Atherosclerosis and arterial degeneration 5
- Liver transplantation 5
Women are affected 4 times more frequently than men 5, though recent large cohorts show 70-81% female predominance 6, 7.
Clinical Presentation
Approximately 80% of splenic artery aneurysms are asymptomatic and discovered incidentally on abdominal imaging 2. When symptomatic, patients present with:
- Chronic upper abdominal or flank pain (20% of cases) 2, 4
- Acute rupture with bleeding (most common reason for emergency presentation) 3, 4
- Pulsatile epigastric mass 5
Rupture Risk and Mortality
The mortality data is stark and drives management decisions:
- Non-pregnant patients: 10-25% mortality with rupture 2
- Pregnant patients: Up to 70% maternal mortality and >90% fetal mortality with rupture 2
- Elective intervention: 0-0.5% mortality 8, 4
- Emergency intervention for rupture: 25-40% mortality 2
The natural history shows that most aneurysms remain stable (78% in systematic reviews), with minimal growth rates of 0.04-0.05 cm/year 6, 7. However, rupture has occurred in aneurysms <2 cm 6, justifying the 2 cm intervention threshold.
Diagnostic Approach
CT angiography is the diagnostic modality of choice 3. Key imaging features to document:
- Aneurysm diameter (critical for management decisions)
- Location (hilum, distal, mid, or proximal splenic artery)
- Morphology (saccular 72% vs fusiform)
- Calcification pattern (88% have calcifications; circumferential calcification predicts reduced growth) 6, 7
- True aneurysm vs pseudoaneurysm
- Presence of mural thrombus
- Parent artery anatomy
Management Protocol
Class I Indications (Must Intervene):
Open repair or catheter-based intervention is indicated for:
- Aneurysms ≥2.0 cm in women of childbearing age who are not pregnant 1
- Aneurysms ≥2.0 cm in patients of either gender undergoing liver transplantation 1
- All symptomatic aneurysms regardless of size 1
- All ruptured aneurysms (immediate intervention) 3, 4
- All pseudoaneurysms (false aneurysms) should be treated 9, 4
Class IIa Indications (Probably Should Intervene):
Open repair or catheter-based intervention is probably indicated for:
- Aneurysms ≥2.0 cm in women beyond childbearing age 1
- Aneurysms ≥2.0 cm in men 1
- Enlarging aneurysms on surveillance 8, 9
Conservative Management (Surveillance):
For asymptomatic aneurysms <2.0 cm in low-risk patients:
- Initial surveillance: CT or ultrasound yearly for 3 years 6
- Extended surveillance: If stable, increase intervals to every 2-3 years 6
- Risk factors requiring closer monitoring: Prior tobacco use (independently predicts growth), portal hypertension, female sex, size >1.4 cm 6, 7
- Protective factors: Circumferential calcification (predicts reduced growth) 6
Treatment Modalities
First-Line: Endovascular Therapy
Endovascular embolization should be the first-line therapy 3, 8, 9. This approach offers:
- 0.5% mortality rate (vs 4.9% with open surgery) 8
- 94.7% technical success rate 10
- 25% perioperative complication rate 10
- 0.9% reintervention rate 10
Endovascular options include:
- Sac embolization (most common)
- Covered stent implantation
- Artery embolization
- Combination techniques based on aneurysm anatomy 10
Open Surgery:
Reserved for:
- Endovascular failure or anatomically unsuitable cases
- Hemodynamically unstable patients with rupture
- Multiple aneurysms requiring complex reconstruction 5
Surgical options:
- Splenectomy with/without distal pancreatectomy (most common historically) 4
- Splenic preservation techniques (endo-aneurysmorrhaphy, ligation) when feasible 5
- Simple ligation if collateral circulation adequate 2
Laparoscopic Surgery:
May be considered in stable, elective cases, though mortality rates are comparable to open surgery (no statistical difference: F(2.71) < F crit(3.02), P=0.07) 8.
Critical Pitfalls to Avoid
Do not delay intervention in women of childbearing age with aneurysms ≥2.0 cm, even if asymptomatic - the catastrophic rupture risk during pregnancy (70% maternal, >90% fetal mortality) mandates prophylactic treatment 2, 1
Do not observe pseudoaneurysms - all false aneurysms require treatment regardless of size due to higher rupture risk 9, 4
Do not assume small size equals safety - ruptures have occurred in aneurysms <2 cm 6
Do not miss pancreatitis as the underlying cause - it's the most common etiology of pseudoaneurysms and may require concurrent management 3, 4
Ensure adequate follow-up after endovascular repair - while reintervention rates are low (0.9%), periodic surveillance is necessary 10
Special Populations
Pregnancy:
- Known aneurysms ≥2.0 cm discovered during pregnancy represent a management dilemma - the natural history through pregnancy is unknown due to lack of large series 2
- Multiple case reports document rupture of 2.0+ cm aneurysms during pregnancy 2
- Prophylactic treatment before conception is strongly preferred for women of childbearing age 1
Liver Transplant Candidates:
- Mandatory treatment of all aneurysms ≥2.0 cm before transplantation 1
- Post-transplant immunosuppression and portal hypertension increase rupture risk
Tobacco Users:
- Only independent predictor of aneurysm growth on multivariate analysis (P=0.028) 7
- Requires more aggressive surveillance and lower threshold for intervention